Effects of fuel reduction treatments on movement and habitat use of American toads in a southern Appalachian hardwood forest

Abstract

Prescribed fire is a commonly used management technique for maintaining fire-adapted ecosystems, yet empirical data regarding its effects on amphibians are limited and contradictory. Anurans (frogs and toads) may be the amphibian taxa most negatively affected by fire due to their extensive use of the forest floor; however, short-term abundance studies suggest that terrestrial toads (e.g., Anaxyrus [Bufo] americanus) may benefit from fire-based ecosystem management. We used radio-telemetry to examine the effects of prescribed fire on movements, home range characteristics, mortality, and habitat selection of A. americanus in a southern Appalachian upland hardwood forest. We tracked 26 adult A. americanus between 27 January and 30 May 2012. Toads exhibited high non-breeding site fidelity and traveled 993.5m (±265.9m) mean (±SD) route distance between the breeding ponds and the last recorded location within their summer habitat. We found no evidence of direct mortality of A. americanus from a prescribed fire that occurred on 13 February 2012. Forward stepwise discriminant analysis (DA) revealed that the availability of coarse woody debris (CWD) was a significant discriminator between microhabitats used (i.e., location plots) and random plots (Wilk’s lambda=0.9852, F1, 661=9.9414, p=0.002). Forward stepwise DA revealed that burned and unburned location plots were significantly different (Wilk’s lambda=0.2713, F1, 221=593.6863, p<0.001) based on the percent of plot ground cover comprised of charred material (%char). When %char was excluded from the analysis due to its short-term nature, the percent of plot ground cover comprised of deciduous leaves, a cover item commonly used by toads in unburned locations, was the variable with the most discriminatory power (Wilk’s lambda=0.4243, F1, 221=299.8741, p<0.001). Toads maintained greater distances from CWD in the unburned (mean±SD=119.50±109.64cm) than in the burned locations (mean±SD=86.05±104.81cm; χ12=9.7055, p=0.002). Our results indicate that prescribed fire as implemented in this study did not cause direct mortality, nor did it appear to inhibit migratory movements of adult A. americanus. However, fire reduced the diversity and availability of refugia, especially deciduous leaves, though the availability of alternative cover objects (e.g., CWD) in burned treatments allowed toads to inhabit those areas, suggesting the importance of noncombustible or semi-permanent refugia for A. americanus in fire-managed forests.